Study of Mural Painting on Mud Plaster: “Los Escudos” from Tehuacán–Ndachjian

The “Los Escudos” mural at the Late Postclassic site known as Tehuacán–Ndachjian in Puebla, Mexico, is relatively unknown within Mexico due to there being limited access to the site, which is situated underground on a mountain. This study describes the first unique opportunity to analyse mural painting samples on mud plaster from this archaeological site. Small, pigmented samples were analysed using optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The compositional and structural characterisation of the samples revealed a stratigraphic composition without a lime plaster layer in addition to the presence of minerals, such as hematite, goethite, palygorskite, gypsum, and feldspars. These findings support the conclusion that the “tempera on earth” pictorial technique with mineral pigments was used to create the mural. The overall results provide valuable data concerning the types of materials and techniques that were used and serve as a reference for conservators in addressing preservation, conservation, and restoration issues for mural paintings on mud plaster. Furthermore, the study enhances understanding of ancient painting techniques on mud plaster and the technological advances that were developed by pre-Hispanic cultures in Mexico.